In crystalline deposits of the mineral magnesite, the MgCO.sub.3 is frequently replaced in part by ferrous carbonate. When this constituent exceeds about 5%, the mineral is termed breunnerite. Typically, such deposits contain about 6 to 9% FeO and although they are often mined for use in making refractories, they are unsuitable for manufacture of commercially pure magnesium compounds such as magnesium sulphate and magnesium chloride.
Breunnerite also occurs in association with other minerals, for example, in talcs of which the breunnerite content may contain as much as 12% FeO and may be associated with other minerals such as pyrrhotite, gersdorffite, pyrite, cobaltite and smalite. In the beneficiation of such minerals to recover talc, tailings are produced which are principally breunnerite associated with varying proportions of these associated minerals. The magnesium carbonate content of these tailings may be 60 to 80%, but because of the many impurities contained, the tailings have not hereto found any commercial use either for refractory manufacture or as a raw material for the manufacture of magnesium compounds.
It is an objective of the present invention to provide a simple process for the recovery of commercially pure magnesium compounds from breunnerite or from tailings of concentrates containing breunnerite.